I have also said, many times on this forum, that there are in fact many things that I do believe, with or without what might be called real evidence. This is true for every human alive. We can't function without our beliefs. My treatment of others, for example, is informed by my attachment to the humanist philosophy. I can't prove the basic tenets of humanism, but I accept them. To give the very short version of what that is, I think of humanism as an outlook or system of thought (which you are free to call "beliefs") attaching prime importance to human rather than divine or supernatural matters, and stressing the potential value and goodness of human beings, emphasizing common human needs, and seeking solely rational ways of solving human problems.
So, if somebody comes to me and says, "you should treat others kindly because that's what God wants, and if you don't, you'll go to Hell," I can reply, "sorry, I don't believe that -- I treat others kindly because that is the right thing to do for me, and I don't expect a heavenly reward for not doing so, nor do I expect to be punished if, in a merely human moment, I fail to live up to my own ideals." That is not caused by atheism. Atheism doesn't figure into why I treat people the way I do. I am driven by my carefully and long-thought about, philosophy. In the absence of any "rules" from some supernatural source, I have had to think about who I am, and what it means to be me in the world in which I find myself.
So if you think that, for me, atheism is "a belief system," as you put it, then you have to tell me how that systems informs my actions. What does not believing in God make me feel I must do? (My own answer is: nothing, I don't consider a deity in anything that I do, with the single exception of answering those who insist that I should think of a deity.)